Fuel supply pump



1962 R. J. WIRSCHING 3,

FUEL SUPPLY PUMP Filed July 6, 195a INVENTOR. ROBERT J. WIRSCHING uwauwwzy A TTORNE United States Patent Office 3,067,688 Patented Dec. 11,1962 3,067,688 FUEL SUPPLY PUMP Robert J. Wirschiug, Korntal, Stuttgart,Germany, assignor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Filed July 6, 1959, Ser. No. 825,042

Claims priority, application Germany July 15, 1958 4 Claims. (Cl. 10337)The present invention relates to a further development and improvementof fuel supply pumps for internal combustion engines provided with asupply piston member located within the pump cylinder.

In the pump constructions known in the prior art, the supply piston isarranged as a plunger member co-axial with respect to the oppositelydisposed pump piston. However, these prior art constructions entailedthe disadvantages of an undesirable, relatively large structural lengthand relatively small pump and supply piston diameters.

The present invention obviates the disadvantages encountered in theprior art constructions by providing a pump piston which is effectivealso directly as supply piston, a feature which is achieved bysubjecting the pump piston, on the one hand, to the influence or actionof an outer supply spring for the pressure stroke thereof and, on theother, subjecting the piston to the influence or action of an innerspring arranged within the pump cylinder for the suction stroke thereofwhich inner spring rests with the end thereof facing the piston againstan entrainment abutment member, arranged directly in front of thepiston, of a plunger or push rod supported within the piston in a mannerto be axially displaceable with respect thereto whereby a controlarrangement, of any known construction acts against the end of theplunger or push rod protruding beyond the piston and pump housing.

Accordingly, it is an object of the present invention to provide a fuelsupply pump construction which obviates the disadvantages of the priorart devices.

It is another object of the present invention to provide a fuel supplypump arrangement which is simple in construction, which utilizes onlyrelatively few parts, and which requires a relatively smaller space thanthe prior art devices.

Still another object of the present invention is the provision of a fuelsupply pump which is compact and utilizes a single piston member forfilling the twofold purposes of suction and supply action.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows in thesingle FIGURE thereof, for purposes of illustration only, one embodimentin accordance with the present invention.

Referring now to the drawing which shows in the single figure thereof across sectional view through a fuel supply pump in accordance with thepresent invention, reference numeral 1 generally designates the T-shapedpump housing which is provided with a suction line 2 and a pressure line3 arranged opposite each other essentially co-axially. The pump cylinder4 provided in the housing 1 is thereby arranged essentiallyperpendicularly to the suction and pressures lines 2 and 3. Onespring-loaded check valve 5 and 6 each is arranged in front of thesuction and pressure line 2 and 3 as seen from within the pump cylinder4. A piston 7 provided with a central bore is adapted to reciprocatewithin the pump cylinder 4 whereby the piston 7 is supported on aplunger or push rod 8 extending through the central bore provided in thepiston 7 in such a manner as to be axially displaceable with respectthereto. An entrainment abutment member 9 is mounted on the inner end ofpush rod 8 in front of the inner end of piston 7 facing the pump spacewhich entrainment abutment member 9 simultaneously is constructed toform the abutment for fro movements under the influence of such controlmechanism and under the influence of the spring 10.

The spring force of the spring 19 may also be appropri ately adjusted bya threaded cap 13 closing off the pump cylinder 4. An overflow orreturn-flow bore 14 is arranged within the range of valving movement ofthe piston 7 which bore is released or opened up by the piston '7 whenthe latter approaches its outermost storing or supplying position inorder to prevent excessive pressures to build up within the pump housing1, for example, if the discharge of the sucked-in fluid quantitiesbecomes zero at the pressure line 3.

OPERATION The operation of the fuel supply pump in accordance with thepresent invention is as follows:

During normal fuel consumption, the pump supplies the amount justrequired therefor. The pressure stroke is thereby realized by the factthat during immersion of the plunger or push rod 8 into the pump space,i.e., during the upward movement thereof as seen in the drawing, theabutment member 9 arranged in front of the piston 7 is taken along andthereby also recedes upwardly; the piston 7 follows such upward movementof the abutment member 9 under the influence of the spring force exertedby spring 11 whereby the spring force decreases with the expansion ofspring 11 up to a point Where the spring force of spring 11 isefiectively insufiicient to move the piston 7 further in the upwarddirection thereof. On the other hand, with the inward, i.e., upwardmovement of the plunger or push-rod 8 caused by the external controlmeans, the spring 10 has been compressed to such an extent that theforce thereof now exceeds the other relatively weak or spring force ofspring 11. Corresponding to the cessation of the external control forceeffecting the inward or upward movement of the plunger member orpush-rod 8, the spring 10 which now seeks to untension itself, againforces the abutment member 9 together with the piston 7 outwardly, i.e.,in the downward direction as viewed in the drawing. As a result thereof,the piston 7 carries out the suction stroke.

If now the consumption of the supplied fuel quantity decreases in line3, then the excess of the sucked-in fluid quantity is accommodatedwithin the pump cylinder by the pump piston 7 in that the latter underthe continu ously increasing compression of the supply spring 11, evermore recedes with respect thereto, i.e., ever more moves downwardly withrespect thereto, until it finally is lifted off the abutment member 9and from then on no longer carries out any reciprocating pumpingmovement at all after the pump movement had previously continuouslydecreased or become ever smaller. If the discharge at the pressure line3 becomes zero or if the piston 7 reaches its outermost, i.e., lowermostsupply end position, then the overflow bore 14 is released or opened upby piston 7 in order to avoid an excess pressure withacezsss in the pumpspace which might damage the pump housing 1. As soon as more fiuidpressure again flows oil into the pressure line 3, the supply piston 7again moves upwardly into the pump space to the extent that the pumpspace becomes free by the fuel discharged through pressure line 3 untilpiston 7 again abuts against the abutment member 9 and resumes itspiston operation.

While I have shown and described one embodiment in accordance with thepresent invention is is understood that the same is not limited theretobut is susceptible of many changes and modifications within the spiritand scope of the present invention and I, therefore, do not wish to belimited to the particular details described and shown herein but intendto cover all such changes and modifications as are encompassed by thescope of the appended claims.

What is claimed is:

1. A pump, especially a fuel supply pump for internal combustionengines, comprising, pump cylinder means including a suction inlet and apressure outlet, check valve means in both said suction inlet and saidpressure outlet, and piston means movable within said pump cylindermeans, said piston means being efiective as a suction and a dischargeassembly and including a piston having a bore extending therethrough,first spring means disposed on one side of said piston and second springmeans disposed on the other side of said piston, abutment means disposedwithin said pump cylinder means adjacent said other side of the pistonand operatively connected to said second spring means, said first springmeans being operative to move said piston in one direction and saidsecond spring means being operative indirectly to move said piston meansthrough movement of said abutment means, and push rod means freelyslidable in said bore and operatively connected with said abutment meansto lift the same from said piston in opposition to said second springmeans and accordingly control operation of said piston means.

2. A pump as defined in claim 1, wherein said pump cylinder meansincludes an overflow bore provided therein within the area of saidpiston means, said overfiow bore being valved by said piston means andbeing opened when said piston means is in the end position in thedirection of the suction stroke of the pump.

3. A pump as defined in claim 2, further comprising means for adjustingthe spring force of said second spring means.

4. A pump, especially a fuel supply pump for an internal combustionengine having means for driving said pump, comprising a pump cylinderhaving a suction inlet and a pressure outlet, check valves in both saidsuction inlet and said pressure outlet, and pump means effective as asuction and supply means arranged within said pump cylinder, said pumpmeans including a piston slidable in said pump cylinder, said pistonhaving a bore extending therethrough, a push rod slidably arrangedwithin said bore, an abutment member disposed adjacent the side of saidpiston facing the interior of said pump cylinder, said push rodextending through said piston and being operatively connected to saidabutment member, a first spring arranged within said pump cylinderoperative to press said abutment member against said piston, and asecond spring operative to press said piston against said abutmentmember, said first spring having a stronger spring force than saidsecond spring, said push rod being adapted to be reciprocably driven insaid bore by said driving means and said first spring to thereby effectthe pressure and suction strokes of said pump means.

References Cited in the file of this patent UNITED STATES PATENTS1,369,915 Church Mar. 1, 1921 1,589,246 Scott June 15, 1926 1,781,404McNab Nov. 11, 1930 l,829,451 McNab Oct. 27, 1931 1,883,459 Auigdor Oct.18, 1932 1,915,832 Mantle June 27, 1933 1,981,667 Rockwell Nov. 20, 19341,984,614 Welch Dec. 18, 1934 2,183,510 Thomas Dec. 12, 1939 2,301,435Mercier Nov. 10, 1942 FOREIGN PATENTS 260,175 Great Britain Oct. 28,1926 318,461 Italy July 13, 1934 375,048 Great Britain June 23, 1932772,507 France Oct. 31, 1934

